Protective layers in AC plasma display panels (PDP) are usually formed by vacuum vapor deposition or sputtering. It is important to study the protective MgO layer by means of screen-printing for fabricating a large size PDP and reducing its cost. With the objectives of enlarging the panel size and reducing cost, we studied the fabrication of the protective MgO layer by means of screen-printing. In this study, we succeeded in lowering the drive voltage by using a MgO powder prepared by vapor phase oxidation instead of conventional decomposition of the magnesium salt. Further, by adding a MgO liquid binder, we attained a good luminous efficiency twice as high as that attained with a sputtered protective layer and lowered the drive voltage. When this protective layer was combined with He-Xe gas enclosure, the half-life of luminance was 5,000 hours. With Ne-Xe gas, the luminance deteriorated no more than 40% after 5,000 hours. A screen-printed protective MgO layer containing no MgO liquid binder showed a short half-life of 800 hours even with the use of Ne-Xe gas. In this case, the discharge voltage changed greatly and some cells did not discharge. It is concluded that the combination of an ultrafine MgO powder prepared by vapor phase oxidation and a MgO liquid binder can clear the way for making AC PDPs with a long lifetime, high efficiency, and low voltage a practical reality.